Temperature, habitat size, and the strenght of biotic interactions

An expanding branch of ecology, called metabolic ecology, attempts to understand and model the role of metabolism in driving ecological processes.

Brown et al.’s Metabolic Theory of Ecology (MTE) states that virtually all characteristics of organisms vary predictably with their body size, temperature and chemical composition, according to the general equation:

I=i0M3/4e-E/kT

This is a complicated and very sciency way of saying that metabolic rate (basically, the rate at which an organism transforms food in energy) increases exponentially as temperature gets higher.

As metabolism gets faster, lots of other things speed up: organisms grow faster, reproduce faster, thus require more food. This may lead to many consequences at the ecological level: population dynamics may be faster, competition among organisms eating the same resources may become harsher, predator-prey interactions may get stronger.

All this, in turn, may lead to less stable biological communities and more likely extinctions.

What I am doing is testing the relative importance of temperature and habitat size in driving population and community dynamics (for the effect of temperature on extinction risk, check out the work of my friend and colleague Chris Clements).

I address my questions experimentally using microcosms (simple artificial ecosystems) with protist communities. Protists are small, single-celled eucariotic organisms which live in water. To be single cells, they are astonishingly complex. Some of them are photosynthetic, like plants, while others eat grazing bacteria or predating other protists. Some are immobile, others swim around thanks to cilia or flagella. They are very diverse: some are ball- or bean-shaped, others are star-shaped, others again look like funnels or have proboscis (here and here, plenty of amazing photos).

Being single cells, they grow fast enough to allow the observation of their population and community dynamics in a short time. On the other hand, they allow insights that can help understanding other organisms and “macroscopic” systems.

(Photo: two Paramecium caudatum cells chatting about the weather. Each is about 100 micrometers long, that is one tenth of a millimeter)